1. Field of the Invention
The present invention relates generally to methods for executing and controlling liquid delivery processes.
2. Discussion of the Background Art
Such systems generally serve for any biological, chemical, and/or physical synthesis analysis or dosage process. The system performance and the quality of the performance of the synthesis analysis or dosage processes, depend, along with other influential factors, on the system pressure and the flow rate of a liquid delivery system. Very common are, for example, High Performance Liquid Chromatography systems. HPLC is a form of chromatography used to separate compounds that are dissolved in liquid. For this purpose, the liquid can be delivered in a more or less constant flow, for example, by a binary pump as disclosed in the EP0309596A1. Such a binary pump can generate an uninterrupted and constant flow of liquid. Besides this, it is possible to generate a solvent gradient.
Sensors, for example pressure sensors and flow rate sensors, can be employed for measuring the process values during liquid delivery. Known are flow rate sensors measuring a pressure drop across a fluidic restriction, for example as disclosed in the paper: “A High-Precision Piezoresistive Flow Sensor for Microdosing Applications” of Marc Boillat, Bart van der Schoot, and Bastien Droz, Seyonic S A, published on the Internet under http://www.sensorsmag.com/articles/0900/129/main.shtml.
Other flow rate sensors comprise a heating element and measure a temperature difference within the flowing fluid upstream and downstream of the heating element. Such sensors are disclosed for example in the paper: “A precision thermal mass flow sensor for small liquid flows” of Ir. H. J. Boe and Ing. W. Derks; published on the Internet under http://www.bronkhorst.com/pdf/thermal.pdf, and are delivered, for example, by the company Sensirion AG, Eggbuehlstrasse 14, CH-8052 Zurich, Switzerland, http://www.sensirion.com.